Various types of septic systems employing peat are known in the prior art. Most prior art peat filtration devices load the effluent from the top of the filter, and allow it to drain down through the peat in order to effect filtration of the effluent. For example, Boyd et al. (U.S. Pat. No. 5,049,265) entitled “Effluent Treatment System” discloses a system for secondarily treating wastewater through a peat filter in which liquid waste from a septic tank is pumped onto the top of a treatment medium consisting of peat. The effluent is collected at the bottom of the peat filter. The system incorporates peat-based organic fibrous material having a relatively low absorptive capacity to promote drainage, and also uses an effluent distribution system to distribute effluent over the filter medium.
Festa et al. (U.S. Pat. No. 6,620,321) entitled “Biofilter System and Method For Treating Wastewater” describes a similar system in which effluent is pumped onto the filter from the top through sacks containing filtering material (often peat), and is allowed to drain out the bottom.
Albert (U.S. Pat. No. 6,506,298) entitled “Biofiltering System for Treating Wastewater Effluent” describes a method for treating effluent that allows continuous treatment. The effluent flows onto the top of a peat layer via a fluid flow regulator, and is permitted to drain into the ground below. A fluid flow regulator and distribution system disposed upstream from the peat ensures that the wastewater flows through the peat bed at a rate no greater than the peat bed biofiltering capacity.
Many effluent treatment systems which incorporate the use of plants are also know in the prior art. Simmering et al. (U.S. Pat. No. 5,690,827) entitled “Sewage Treatment System Using Peat and a Constructed Wetland” discloses a three-stage method of sewage treatment consisting of primary settling, passing the effluent through a peat filter, and then passing the filtered effluent through a sub-surface constructed wetland. In this method, the plants are used as a separate stage of treatment following passage through the peat filter.
Winters (WO 98/21153) entitled “Device for Cleaning Polluted Water” describes a method for treating water in a mobile container filled with multiple layers, including porous layers at the bottom of the container, a layer of peat, and then a layer of sand above the peat. The method includes the use of plants for purification, particularly reeds. The container is mobile so that it may be easily replaced. Effluent is pumped into a layer of sand near the top of the reservoir, and is collected by a discharge pipe located in the base of the container. The container is flooded to a certain level to create an appropriate ground water level to promote the activity of microorganisms at the interface between wet and dry soil.
Rambeck (WO 99/32406) entitled “Improved Effluent Treatment System” describes a two-stage treatment system, to treat both solid and liquid portions of effluent. The treatment is provided by gravel in layers, with microorganisms in the gravel, and plants. Solids are retained on top of the filter body, to be transformed into a soil-peat structure, while the liquid percolates through the filter for purification.
Wolverton (U.S. Pat. No. 4,415,450) entitled “Method for Treating Wastewater Using Microorganisms and Vascular Aquatic Plants” describes a system in which supernatant from a settling tank is pumped into the bottom of a container filled with rocks, pea gravel, and vascular aquatic plants for treatment. Effluent is purified by flowing upward through the tank, during which time it is subject to processing by anaerobic and facultative microorganisrns, and the roots of at least one vascular aquatic plant.
While numerous effluent treatment systems are known in the prior art employing peat or vascular plants, they are not specifically sized and configured for tertiary effluent treatment or to accommodate both periodic surges in effluent flow and periods of low flow. Domestic wastewater production is typically uneven, with peak flows in the morning and early evening. Conventional treatment systems are typically under loaded for most of the day and overloaded for brief periods. Additionally, secondary treatment alone is insufficient to remove microcontaminants and nutrients. The need has therefore arisen for an improved tertiary filter system employing peat or other peat-like organic or synthetic materials which can operate continuously and passively, even during periods of low effluent inflow.